How To Lookup For That Unknown Caller

How To Lookup For That Unknown Caller: "I was sleeping one day and I was abruptly woken up by a beep from my phone. When check what is it on my phone, I saw that it was a message from someone and when I try to check who the sender of the text message is, I discovered that it was not in my phone s phonebook and I decided to ignore the text message and even the unknown sender and I went to"